Stress in Beams - Same Force, Same Area, Different Lengths

In summary, the max stress is the same for both types of stress because they are under the same force.
  • #1
Victor.wong
5
0
if you look at the attached photo.

we have 2 beams, 1) is shorter, 2) is longer. cross-sectional area is the same. same force is applied X cm from the fixed end.

what is the max stress in each case? why are they the same ( and why not)?

Take gravity out of the equation.
FEA shows differnt result.
 

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  • #2
victor.wong
what is the max stress in each case? why are they the same ( and why not)?

Hello victor, is this a lab experiment you are writing up?

You surely don't need a finite element analysis to distinguish between types of stress, this is more fundamental than FEA.

So what do you mean by max stress?

Do you know how to derive stress as a function of distance?
 
  • #3
How different is "different"? Beam theory is only an approximation. A 3-D finite element model is a different approximation. You wouldn't expect them to be "exactly" the same.
 
  • #4
I know it is a very simple question. but FEA is telling me sth i don't expect. so ask this equation and see who can explain.

first of all, stress only caused if a block of material is under 2 force. action force and reaction (the fixture). since the length under the point of force of action is not under another reaction force. these length should not affect the stress produced by this action force

in both cases, max stress appeared at the area around the top fixing point. if i let the applied force and location constant, changing the length of the block will change the max stress at the fixing area. why??
 
  • #5
Well what do you mean by max stress?

Or if you like, what type of stress?

And how about answering my other questions, they were intended to help.
 
  • #6
OK. may be a pic will explain more

if you see the new attachment, my question is, why is the length of the block below the applied force affect the stress at the circled area.

my thinking behind is, no matter how long the rod is below the force application. it should not affect the portion on top of the applied force.

right? and why?
 

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  • #7
Do you know the difference between bending stress and shear stress?
 

1. How does the length of a beam affect stress?

The length of a beam directly affects the amount of stress it can withstand. Longer beams experience more stress due to the same force being applied over a larger area, resulting in a higher amount of bending and tension.

2. Why is it important to consider the length of a beam when analyzing stress?

The length of a beam is an important factor to consider when analyzing stress because it can significantly impact the structural integrity and safety of the beam. If a beam is too long for a given force, it may fail or deform under stress.

3. How does stress vary between beams with the same force and same area but different lengths?

The stress in a beam with the same force and same area but different lengths will vary based on the length of the beam. A longer beam will experience higher stress due to the force being spread over a larger area, while a shorter beam will experience lower stress due to the force being concentrated over a smaller area.

4. How can we reduce stress in a beam with the same force and same area but different lengths?

To reduce stress in a beam with the same force and same area but different lengths, we can either decrease the force applied or increase the area of the beam. Another option is to decrease the length of the beam, which will decrease the amount of bending and tension it experiences.

5. Can the same beam with different lengths experience different types of stress?

Yes, the same beam with different lengths can experience different types of stress. A longer beam may experience more bending stress, while a shorter beam may experience more compression stress. The type of stress experienced depends on the length and geometry of the beam, as well as the direction and magnitude of the force applied.

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